// Package main is the entry point for the webhooker application.
package main

import (
	"fmt"
	"io"
	"os"
	"time"

	"go.uber.org/fx"
	"go.uber.org/fx/fxevent"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/datadir"
	"sneak.berlin/go/webhooker/internal/delivery"
	"sneak.berlin/go/webhooker/internal/globals"
	"sneak.berlin/go/webhooker/internal/handlers"
	"sneak.berlin/go/webhooker/internal/healthcheck"
	"sneak.berlin/go/webhooker/internal/logger"
	"sneak.berlin/go/webhooker/internal/metrics"
	"sneak.berlin/go/webhooker/internal/middleware"
	"sneak.berlin/go/webhooker/internal/resetpw"
	"sneak.berlin/go/webhooker/internal/server"
	"sneak.berlin/go/webhooker/internal/session"
)

// stopTimeout bounds the whole fx stop sequence, not each hook.
//
// fx defaults to 15s, which is longer than Docker's 10s default
// stop grace: the container would be SIGKILLed before the bound
// could fire, so nothing bounded by it would ever be observed.
// 5s leaves headroom inside that grace for signal delivery and
// process exit; the observed wedge case already exits at ~5.3s,
// so a larger bound would trade a rare skipped database close for
// a more common hard kill.
//
// The server's stop hook must fit inside it with room to spare: a
// hook that used the whole budget would exhaust it at that instant,
// and fx would skip every hook after the server — the delivery
// engine, the healthcheck, the webhook DB manager and the database
// close. That hook is the 3s HTTP drain plus the Sentry flush that
// follows it in the same hook, so the flush is clamped to the stop
// context's remaining time less server.TailHookReserve rather than
// running for its own fixed 2s; the reserve is what the tail hooks
// live on, and they are microsecond-scale in normal operation.
// TestStopTimeout_LeavesHeadroomForTailHooks pins the arithmetic
// across every drain length.
//
// This does not make the database close unconditional: the
// ArchiveSweeper and RetentionReaper hooks run before the server
// and can still consume the whole budget on their own.
const stopTimeout = 5 * time.Second

// exitUsage is the status for a command line this binary cannot make
// sense of, kept distinct from the 1 a refusal exits with so that a
// caller can tell "called wrong" from "declined".
const exitUsage = 2

// helpCommand is the subcommand that prints usage. The flag spellings
// beside it in the switch are aliases; this is the name the usage text
// documents and the one tests invoke.
const helpCommand = "help"

// Build-time variables set via -ldflags.
//
//nolint:gochecknoglobals // Build-time variables injected by the linker.
var (
	version = "dev"
	appname = "webhooker"
)

func main() {
	globals.Appname = appname
	globals.Version = version

	os.Exit(dispatch(os.Args[1:], os.Stdin, os.Stdout, os.Stderr))
}

// dispatch routes the command line to a subcommand.
//
// No arguments runs the server, which is what the image's CMD and
// every existing deployment invoke; that path is unchanged, including
// where the DATA_DIR lock is taken relative to building the fx graph
// and how fx propagates a non-zero exit itself.
//
// The optional .env file is read here, before any subcommand and so
// before anything reads the environment — config.DataDir, which both
// the DATA_DIR lock and resetpw call outside the fx graph, above all.
// It used to be read from an init() in internal/config, which put it
// earlier still but threw the error away: a single malformed line
// applied none of the file and said nothing about it. A file that is
// not there stays fine, since .env is optional and most deployments
// do not have one.
func dispatch(
	args []string,
	stdin io.Reader,
	stdout, stderr io.Writer,
) int {
	err := config.LoadDotEnv()
	if err != nil {
		_, _ = fmt.Fprintf(stderr, "%s: %v\n", appname, err)

		return 1
	}

	if len(args) == 0 {
		return run(stderr)
	}

	switch args[0] {
	case resetpw.Name:
		return resetpw.Run(args[1:], stdin, stdout, stderr)
	case helpCommand, "-h", "-help", "--help":
		usage(stdout)

		return 0
	default:
		_, _ = fmt.Fprintf(
			stderr, "%s: unknown subcommand %q\n", appname, args[0],
		)
		usage(stderr)

		return exitUsage
	}
}

// usage lists what the binary can be asked to do.
func usage(w io.Writer) {
	_, _ = fmt.Fprintf(w, `usage: %s [subcommand]

With no subcommand, runs the webhooker server.

Subcommands:
  %s [-generate] <username>
        Set an existing account's password on a stopped deployment.
        Recovers an admin account whose bootstrap password was lost.
  help
        Print this message.
`, appname, resetpw.Name)
}

// run takes the exclusive DATA_DIR lock, then runs the application
// under it, and returns the process exit status.
//
// The lock is taken here rather than inside the fx graph because it has
// to be held before anything opens a database, and because a refusal
// has to reach the operator as a plain line on standard error rather
// than as one entry in an fx failure dump. It is released by the defer
// on a clean shutdown, and by the kernel closing the descriptor on any
// other exit — including the one fx performs itself when a start or
// stop hook fails, which skips deferred calls.
func run(stderr io.Writer) int {
	lock, err := datadir.Acquire(config.DataDir())
	if err != nil {
		_, _ = fmt.Fprintf(stderr, "%s: %v\n", appname, err)

		return 1
	}

	defer func() { _ = lock.Release() }()

	newApp().Run()

	return 0
}

// newApp builds the application graph. It is separate from main so
// a test can assert the options it carries.
func newApp() *fx.App {
	return fx.New(
		fx.StopTimeout(stopTimeout),
		// fx's own events go through the service's logger, not fx's
		// console logger on standard error. The exception is a failure
		// before this logger is built, such as an invalid configuration
		// value, which fx's console logger still prints there. fx holds
		// its events back until this logger is built and then replays
		// them, so it takes the configuration, which sets the level
		// DEBUG=true asks for: without it the replay would run at INFO
		// and drop every record of how the graph was built.
		fx.WithLogger(
			func(l *logger.Logger, _ *config.Config) fxevent.Logger {
				return logger.NewFxLogger(l.Get())
			},
		),
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
			database.New,
			database.NewWebhookDBManager,
			database.NewRetentionReaper,
			healthcheck.New,
			session.New,
			handlers.New,
			// The registry /metrics serves, and the delivery
			// collectors registered on it.
			metrics.NewRegistry,
			metrics.New,
			middleware.New,
			// The one SSRF guard both target-creation validation
			// and the delivery dialer consult, so they cannot
			// disagree about a destination.
			delivery.NewGuard,
			delivery.New,
			delivery.NewArchiveSweeper,
			// Wire *delivery.Engine as delivery.Notifier so the
			// webhook handler can notify the engine of new deliveries.
			func(e *delivery.Engine) delivery.Notifier { return e },
			// Wire *delivery.Engine as delivery.Archives so deleting
			// or renaming a webhook or target reaches its archive
			// files.
			func(e *delivery.Engine) delivery.Archives { return e },
			server.New,
		),
		fx.Invoke(
			func(
				*server.Server,
				*delivery.Engine,
				*database.RetentionReaper,
				*delivery.ArchiveSweeper,
			) {
			},
		),
	)
}